THETA CORRESPONDENCE AND ARTHUR PACKETS

Abstract

In a joint work with Jialiang Zou, we have established an Arthur's multiplicity formula for even orthogonal or unitary groups with Witt index less than or equal to one. In that multiplicity formula, some local packets defined using the stable range theta lifts are involved. In this paper, we prove that at non-Archimedean places, the definition of the local packets involved in that multiplicity formula are independent of the choice of the dual-pairs used in their construction; moreover, at those places where the groups are quasi-split, we prove that the local packets involved are the same as the local A-packets defined by Arthur/ Mok.